The most dynamic segment of orthopedic and neurosurgical medical practice over the past decade has been spinal devices designed to fuse the spine to treat a broad range of degenerative spinal disorders. Back pain is a significant clinical problem and the annual costs to treat it, both surgical and medical, is estimated to be over $2 billion. Motion preserving devices to treat back and extremity pain has, however, created a treatment alternative to or in combination with fusion for degenerative disk disease. These devices offer the possibility of eliminating the long term clinical consequences of fusing the spine that is associated with accelerated degenerative changes at adjacent disk levels.